The invention concerns a method for stabilizing an artificial patina layer produced on a copper panel.
In the processing of copper panels with an artificial patina layer, it has been found that, in particular when such copper panels are bent, the patina layer at least partially detaches. The chips and dust resulting from this can lead to environmental impacts, in particular to skin irritation and to tool corrosion.
Although efforts have already been made to protect an artificial patina layer with clear varnish, clear varnish cannot be applied until after the "maturing" process of an artificial patina layer is complete. The reason for applying the clear varnish after completion of the maturing process is that clear varnish is not porous enough to allow the maturing process to proceed. The "maturing process" is understood to mean a reaction in which the artificial patina layer is exposed to the atmosphere for a period of approximately one week to several weeks. During this period the crystal structures of the artificial patina then react in combination with atmospheric moisture in such a way that the particular desired patina is achieved in terms of both color and structure.
But even when the clear varnish is applied after completion of the maturing process, it is basically impossible to prevent moisture from migrating under the clear varnish layer from the edges of a copper panel or from the machining edges. The clear varnish layer can then chip and thereby take at least portions of the artificial patina layer with it. Moreover when clear varnish is used it is impossible to prevent it from cracking over large areas, or to prevent hairline cracks in the clear varnish layer through which moisture can penetrate. This again ultimately allows the entire coating, consisting of clear varnish and artificial patina, to be pulled off somewhat like a skin. This would, however, cause the artificially generated patina to disappear.
In order to eliminate the disadvantages referred to above, until now copper panels equipped with an artificial patina layer have usually been reshaped, directly after production of the patina layer, in the manner desired based on the application. The copper panels reshaped in this manner were then exposed to the open atmosphere in order to allow the maturing process to proceed.